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35 lines
1.4 KiB
Racket
35 lines
1.4 KiB
Racket
#lang racket/base
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(require (for-syntax racket/base br/syntax) br/define)
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(provide (all-defined-out))
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;; read "foo bar" the same way as "(foo bar)"
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;; other "bar" is dropped, which is too astonishing
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(define (string->datum str)
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(let ([result (read (open-input-string (format "(~a)" str)))])
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(if (= (length result) 1)
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(car result)
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result)))
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(define-syntax format-datum
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(λ(stx)
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(syntax-case stx (quote datum)
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[(_ (quote <datum-template>) <arg> ...)
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#'(format-datum (datum <datum-template>) <arg> ...)]
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[(_ (datum datum-template) <arg> ...)
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(syntax-let ([#'format-string (format "~a" (syntax->datum #'datum-template))])
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#'(string->datum (apply format format-string (map (λ(arg) (if (syntax? arg)
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(syntax->datum arg)
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arg)) (list <arg> ...)))))])))
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(module+ test
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(require rackunit)
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(check-equal? (string->datum "foo") 'foo)
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(check-equal? (string->datum "(foo bar)") '(foo bar))
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(check-equal? (string->datum "foo bar") '(foo bar))
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(check-equal? (string->datum "42") 42)
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(check-equal? (format-datum '(~a-bar-~a) "foo" "zam") '(foo-bar-zam))
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(check-equal? (format-datum (datum (~a-bar-~a)) "foo" "zam") '(foo-bar-zam))
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(check-equal? (format-datum '~a "foo") 'foo)
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(check-equal? (format-datum (datum ~a) "foo") 'foo))
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